The varroa mite (Varroa destructor) was first detected in Portugal in 1986. Since then, there has been a frequent use of amitraz (Apivar, Acadrex) in the attempt to cope with it. Following (i) various credible international reports of increased varroa resistance to amitraz and (ii) regular claims, by national beekeepers, of poor efficacy of Apivar treatments, a large screening project was setup (2003/2004) for trying to identify honey bee colonies hosting varroa populations resistant to amitraz in continental Portugal.